/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineGroupsInterface.h
Ask the server for GroupInfo corresponding to the provided group ID. If this completes successfully, you can call GetCachedGroupInfo to get the full group information. Even if the group info is currently cached, this function will contact the server (ostensibly to refresh the cache).
void QueryGroupInfo ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & ContextUserId, const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & GroupId, const [FOnGroupsRequestCompleted](API\Plugins\OnlineSubsystem\Interfaces\FOnGroupsRequestCompleted) & OnCompleted )